Is this considered pregnancy discrimination?

I found out today I'm being demoted from a higher position. Here's the backstory. Ever since I found out I was pregnant my job has never been supportive. It got so bad because I was going through so many physical changes I couldn't do everything they wanted me to. All my managers threatened to fire me telling me I'm fine I just need counseling. In my first trimester I would have to hide just to throw up from my morning sickness. I'd throw up 3-4 times daily. It got so bad that I put in my 2 weeks notice and then instead of leaving I went down to 2 days a week but because they've refused to do things for me I felt working less was safer and healthier for the baby. Over the past few months I've been doing what I can physically to continue my position. Well today I was told that because of my going to 2 days a week and my "physical demands" I'm being demoted. They are finding someone else to do my job because I cant physically do it and I ask for help and i don't get it. I have to wait 5-10 minutes every time I have to use the bathroom because I have no assistance. I'm left to handle a whole back half of a store on my own while pregnant! Their demands are ridiculous.